... so download Apache OpenOffice from http://www.openoffice.org/download/in.... Create a new user on your PC and install AOO for that user only. AOO and LO seem to interact in that LO grabs some of the AOO properties and this will completely isolate AOO from LO. Open the .docx file with AOO. Save it as a .odt file. Uninstall AOO and delete the added user.

2 Follow the directions given in the AOO forum at ...

... https://forum.openoffice.org/en/forum.... This requires you to unzip the .docx file, extract the \word\document.xml file, and remove all the occurrences of the repeated attribute specified in the error message you get when you open the .docx file.

Note that there may be more than one attribute which is repeated throughout the file so you may have to do this for each of the other repeated attribute(s). Repeated attributes reported include w:themeShade, w:themeColor and w:cstheme. Files have had many (30+?) repeats.

3 Extract \word\document.xml from the .docx file and strip off all the XML tags to leave just the text

This is a "brute force and ignorance" method that strips all the formatting and leaves just the unformatted text, but it should work when everything else fails.